I have some .308 brass (fired 2x) that the bullet can be hand seated/pushed/started into the neck. I do not turn necks. I have had this problem before with some Hornady brass. I measured the neck thickness as best I could with my dial caliper gauge. The problem brass had neck measurements .002-.003 thinner than the good brass. I couldnt find anything else wrong. So I chalked it up to some bad brass. Now I have the same problem with some Winchester nickel plated brass. None of the dies are set up any different than before. I even resized a few times hoping to tighten things up, but no luck. Has anybody had this problem before? I am using RCBS .308Win full length dies. If the outside dia is sized properly, but the inside dia is bigger (thinner necks), is this just bad brass? any help would be greatly appreciated!

The neck size should be set by the expander ball as the case comes out of the sizing die. That assumes the sizing squeezed the neck enough that it has to be expanded slightly. It sounds like the thinner necks don’t get squeezed enough (which you already figured out).

Adjusting your sizing die for the different types of brass would be a big headache. You might want to find a sizing die that uses bushings that can be swapped out easily or buy a second sizing die ($$).

expander ball......just to add some more confusion, I have read that to cure some rough expander ball exits, and to prevent pulling the necks off line, to take some emery cloth and LIGHTLY polish the expander ball. That did help the roughness. But that sure doenst help to explain thinner necks. I will probably just toss the bad brass, but I sure would like to know the exact cause. I will just get some more new brass, rather than new dies, at least until I come up with a reason. I will try to call some brass people today, like Horndady, Federal, etc.

Decap those cases individually, then full length size WITHOUT the expander ball and see how that works. Treat this as a new load and begin with starting loads. If your load is fairly high up the scale, this might give a little more initial pressure than you want. (Probably won't blow anything up, but why takes unnecessary chances?)

Archie, funny you mention decaping. I was lookin at decapping dies today, and thinking the same thing. My .308 loads are pretty mild, so pressures were never really a worry. 44grs. of Varget. Got some more info... as I got to thinking, and jogged my memory. I THINK the brass i have problems with was sized BEFORE I polished my expander ball. I was dealing with concentricity, and read about taking emery cloth and LIGHTLY polishing the expander ball a few months ago. That helped on my recent sizing. I measured my expander ball tonight (after emery cloth) and it was .305 (.003 under .308). I compaired that to my other expander balls from 30-06, .300Win Mag, and 30-30, and they measured .306. So I figured I removed no more than .001 from my .308 expander ball. The problem brass neck thickness measured .010-.011, as compaired to my good brass, .013-.015. I still have 14rds left of that batch, so well see how that resizes with the polished expander ball. If I remember right, when I resized prior to polishing the expander ball, it was pretty rough as the ball passed back through the neck. Thats one of the reasons I ended up polishing the ball, along with trying to get things concentric. Now I just need a day off to go shoot.......thanks everyone for clearing some things up, and rattling my brain. I really need to start a journal, to write things down, like any modifications that were done etc.

How many reloads do you have through these cases? It sounds like they are going into the neck sizing portion of the die, then springing back out to near their fired dimension. I've had that happen with the thin mouth Remington .45 ACP cases. It means the brass has work-hardened and you need to anneal the necks. Even if you find a workaround (no expander), hardened necks will start splitting soon if you don't anneal them.

If the issue is genuinely overly thin neck brass and not annealing (this would mean they never resized properly after their first loading), get a Redding S type sizing die (either FL or Neck Only, as you prefer) or a Forster bushing die. Both use neck bushings you can buy in different sizes to get the neck sizing you need. A less expensive alternative is to by a Lee Collet Die which, with some practice and adjusting, will let you perform a second sizing operation on these cases, pushing only the neck down to the size of its mandrel. If the necks used to resize OK, though, and are springy, you will still have to anneal them to make even this work.

"How many reloads do you have through these cases?" I have only fired/resized this brass 2 times, its nickel as well, something I dont really prefer...I will probably get picking up that Lee collet die this weekend, something Ive been wanting to try for a long time anyway..."You might also check the bullet diameter"...I will double check the actual bullet diameter...Like I said earlier, I THINK this brass was sized prior to my using emery cloth on the expander ball. The batch of brass sized after polishing didnt have any problems, and IF i remember right, they are from the same lot of 20.....I really need to start that journal....now I just need to fire that last batch of brass and see how sizing goes...

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